Rectifier anode bushing



Filed Nov. 16, 1931 Patented Jan. 9, 1934 PATET OFFICE RECTFIER ANODE RUSHING Stefan 'VJidnier and Arthur Gaudenzi, Baden,

Switzerland, assignors Brown Roveri LJ Cie.,

to Aktiengesellschaft Baden, Switzerland, a

joint-steek company of Switzerland Application November 16, 1931, Serial No.

575,439, and in Germany November 12, 1930 3 Claims.

An application has been led in Germany November 12, 1930.

This invention relates to improvements in electric current rectiers of the metallic vapor type and more particularly to an anode structure for such rectiiers.

An electric current rectifier of the metallic vapor type should be kept at a high temperature during operation to prevent condensation of the metallic vapor on the anodes where such condensation may cause short circuiting or backlring within the rectifier. The maintenance of a high temperature in the vicinity of the anodes also causesa decrease in the density of the gases and the vapors about the anodes, due to heat radiation from the anodes, and further decreases the danger of back fires or short circuits. In. the usual electric power rectifier constructions, the anode stem extends through the vwall of the tank in which the rectifying action takes place and is insulated therefrom. The high temperature of the anodes causes the insulator to be subjected to very high temperatures and particularly to a wide range of temperature from the end of the insulator within the tank to the end thereof in contact with the atmosphere. It is well known that the resistance to penetration, of insulators and insulating materials, decreases with increasing temperature and that all insulators substantially lose their insulating qualities at and above 200 C., so that lashovers may take place through the insulators. In a power rectifier, the insulator about an anode is heated to a high temperature particularly in that portion thereof adjacent the anode portion to whichthe arc attaches and is 4cooled at the point of contact of the insulator with the water-cooled tank and by its contact with the atmosphere. In addition to the effects of high temperature on a portion of the insulator as regards its insulating qualities, there is therefore also the effect of heat stresses due to the unequal temperature prevailing throughout the entire structure in addition to the mechanical stresses on the insulator. The result of the above conditons is that failures of the insulators occur which cause disturbances during operation of the rectifier and may even lead to complete destruction thereof.

It is, therefore, among the objects of the present invention to provide means for protecting the insulator about an anode of an electric power rectifier of the metallic vapor type from the heating effect of the anode.

Another object of the invention is to protect the insulator about the anode of an electric power (Cl. Z-27.5)

companying drawing forming a portion of the present disclosure which illustrates one embodiment of the present invention showing an .anode of an electric power rectifier in elevationandan anode bushing structure in vertical section.

Referring more particularly to the .drawingby characters of reference, the reference numeral 1 designates a portion of the top of an electric power rectifier of the metallic vapor type. The vtop is shown as being double walled or jacketed to permit the circulation of a cooling mediumtherethrough and is apertured to permit the extension through the several apertures of a plurality of anodes of which only one is shown. The anode shown comprises an anode head 2 within -the rectifier tank (not shown) to which an arc .is to attach, an anode stem 3 extending through the top l of the rectifying tank and a radiator 4 by which the major portion of the heat created in the anode structure, by the attachment of the arc thereto, is radiated to the atmosphere. The anode structure extends through the aperture in the tcp of the tank in insulated relation therewith and is supported therein. Proper insulation of the anode from the top is obtained by means of an insulator 6 which is a substantially cylindrical member having a plurality of external shoulders '7 and S and an external skirt 9. The insulator is supported in the top l upon a shoulder formed thereon and upon a ring 11 secured on the other side of the top and is sealed in gastight relation with the top by means of a gasket l2 or other suitable means now known to the art. The lower end of the insulator 6 is sealed against the anode head 2 by means of a gasket 13 to prevent the entrance of metallic vapor through the space between the insulator and the anode stem and to aid in sealing such space in gas-tight relation from the interior of the rectifier tank. The top of the insulator 6 extending beyond the top of the rectifier tank is sealed against the anode stem 3 in gas-tight relation by means of a gasket ift or other suitable known means. A guide or shield is supported about the anode head 2 from the skirt 9 of the insulator and extends downwardly from such skirt for the purpose of guiding the arc in its path from the anode to the cathode (not shown) of the rectifier.

The space between the stem 3 and the interior surface of the insulator 6 heretofore permitted the direct transfer of heat from the anode stem 3 to the insulator 6 which was thus subjected to a wide range of temperature variations over the length of the insulator in addition to the mechanical stresses exerted thereon to maintain the anode head 2 in sealing engagement therewith. The present invention provides a shield 16 in the form of a cylinder of highly heat conductive material secured to the anode stem 3 adjacent the upper end thereof and spaced from both the anode stem and the interior surface of the insulator and also from the upper surface of the anode head 2. The heat in the anode stem is received by the shield both by conduction and by transfer across the space between the stem and the shield. Being of highly heat conductive material, the shield 16 is at substantially the same temperature over its entire length. Some of the heat from the shield transfers to the insulator but, due to the high heat conductivity and consequently of the uniform temperature of the shield over its entire length, the amount of heat transferred is reduced and such transfer takes place uniformly over the entire length of the insulator. Such reduction in the amount of heating and the uniformity of the heating retains the insulating value of the insulator 6 at substantially its original value and avoids the occurrence of localized heat stresses therein, The shield 16 is preferably highly polished on both surfaces to secure reflection of the major portion of the heat radiated from the stem and to diminish the degree of heat radiation to the insulator from the shield which effect further reduces the heating effect on the insulator. The life and the insulating value of the insulator 6 are thus both materially increased. The shield may, of course, be coated with any material which will take a high polish and which is not affected by metallic vapor or such shield may be completely made from such material.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made herein without departing from the spirit of the invention or from the scope of the appended claims.

The invention claimed is:

1. In an anode structure for electric power rectiers of the metallic vapor type, an anode having a head portion and a stem portion, a poorly heat conductive electric insulator arranged about the stem portion of said anode and spaced therefrom, and a cylinder of highly heat conductive metal arranged about the stem of said anode in spaced relation therewith and supported therefrom out of contact with the head portion of said anode, the inner and outer surfaces of said cylinder being highly polished to thereby diminish the transfer of heat thereto from the stem of said anode, and to also diminish the transfer of heat therefrom to said insulator.

2. In an anode structure for electric current rectiiiers, an electric insulator having an aperture extending therethrough, an anode having a stem extending through said aperture, means closing the ends of said aperture and supporting said stem in spaced relation with the wall of said insulator defined by said aperture to form a closed annular chamber between said stem and insulator, and a cylinder of material having high thermal conductivity arranged in said chamber in spaced relation with respect to said stem and said wall, the surfaces of said cylinder being highly polished to thereby diminish the transfer of heat from said stern to said insulator and having an end thereof ailixed to said stem for maintaining said chamber at substantially uniform temperature throughout its length.

3. In an anode structure for electric current rectiers, an electric insulator having an aperture extending therethrough, an anode comprising a head portion and a stem portion, the said stem portion extending through said aperture in spaced relation with the wall of said insulator defined by said aperture, means interposed between said anode head and said insulator closing one end of said aperture, means interposed between said stem and said insulator closing the other end of said aperture to thereby form a substantially gas tight annular chamber between said stem and said insulator, and a metallic sleeve of high thermal conductivity arranged in said chamber in spaced relation with said anode head and stem and said wall, the surfaces of said sleeve being highly polished to thereby diminish the transfer of heat from said stem to said sleeve and to diminish the transfer of heat from said sleeve to said insulator, and one end of said sleeve being affixed to said stem and the other end thereof being out of contact with said anode head to thereby maintain the said chamber at substantially uniform temperature throughout its length.

STEFAN WIDMER. ARTHUR GAUDENZI. 

